big problem

[m1ck_b87]

I'm testing street lighting which has 10 sodium lights over a space of about 200m wired in 3 core 4mm armoured underground, this is protected by a 16 amp mcb. I've done a Zs and its greater than the max Zs values for the 60898 type b, what is the easiest way of working out the load.

 

[sparkymalarky]

what rating are each of your lamps in the fitting?

Find out how many lamps you have on the circuit in total and find the total rating of the circuit in Watts (Power)

Power / Voltage = Current.

so say each lamp was 200Watt

2000/230V - 8.69Amps.

 

[m1ck_b87]

What about length of the run obviously rise in resistance will cause the current to rise

 

[sparkymalarky]

did you carry out any tests?

 

[High Tower]

Change the mcb to a RCBO, job done!!

 

[MDJ]

UM, well that could be a problem, I would bet 10 sodium street lights over 200 mtrs of cable would trip haha, m1ck, whats the ZS reading?

 

[m1ck_b87]

Zs reading was 3.64 and it has a contactor I was thinking of down grading to a 10 amp that's why I wanted to work out a accurate load

 

[bigbaddave]

As above.. Another way to comply when ELI value is to high is too???

 

[MDJ]

Ah I see your situation, are the sodiums 70 watt or bigger?

 

[m1ck_b87]

70w sodium lights. Cable calculations are not the easiest aswell

 

[FAA Greenie]

What about length of the run obviously rise in resistance will cause the current to rise

Huh ????

 

[rmc86uk]

I'm testing street lighting which has 10 sodium lights over a space of about 200m wired in 3 core 4mm armoured underground, this is protected by a 16 amp mcb. I've done a Zs and its greater than the max Zs values for the 60898 type b, what is the easiest way of working out the load.

Hi M1ck,

I don't want to seem rude but you are testing street lighting yet asking on a forum how to calculate design current?

 

[m1ck_b87]

FAA greenie huh ?????

 

[Guest111]

whichever way you work it out don,t forget the power used will be a little more than the 70W stated for the lamp,due to losses in the control gear etc,on a single lamp this may not matter but on a run of them well it may be something you need to allow for.

 

[sparkymalarky]

Seems fairly straightforward to me.

 

[cobrauk]

A Test with clamp on amp meter with all the lights running will soon give you the full load,but if the lamps are 70watt the load will be well under 10amps in which case you zs of 3.64 will be fine with a 10amp type B or you could go to a 6amp type C

 

[sparkymalarky]

Test with clamp meter and assess load in reference to the design current for the circuit.
Measure R1+R2.
Measure Zs at distribution board.
Measure Zs at circuit.
Look for any abnormal results across the above ^.
60898 Type B 6Amp or 10Amp will be fine IMO.

 

[daniel198207]

dont forget to zero your leads ;-0

 

[SirKit Breaker]

and check all terminations are tight, free from corrosion etc.

 

[m1ck_b87]

Thanks guys I will invest in a clamp meter